1h6c: Difference between revisions
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'''OXIDIZED PRECURSOR FORM OF GLUCOSE-FRUCTOSE OXIDOREDUCTASE FROM ZYMOMONAS MOBILIS COMPLEXED WITH SUCCINATE''' | '''OXIDIZED PRECURSOR FORM OF GLUCOSE-FRUCTOSE OXIDOREDUCTASE FROM ZYMOMONAS MOBILIS COMPLEXED WITH SUCCINATE''' | ||
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[[Category: Baker, E N.]] | [[Category: Baker, E N.]] | ||
[[Category: Nurizzo, D.]] | [[Category: Nurizzo, D.]] | ||
[[Category: | [[Category: Crystal structure]] | ||
[[Category: | [[Category: Ligand binding]] | ||
[[Category: | [[Category: Periplasmic oxidoreductase]] | ||
[[Category: | [[Category: Protein translocation]] | ||
[[Category: | [[Category: Signal peptide]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 18:29:24 2008'' | |||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | |||
Revision as of 18:29, 2 May 2008
OXIDIZED PRECURSOR FORM OF GLUCOSE-FRUCTOSE OXIDOREDUCTASE FROM ZYMOMONAS MOBILIS COMPLEXED WITH SUCCINATE
OverviewOverview
The NADP(H)-dependent enzyme glucose-fructose oxidoreductase (GFOR) is a classic example of a redox protein that is translocated across a membrane in fully folded form. GFOR is synthesized in the cytoplasm with a 52-residue signal peptide, giving a precursor form, preGFOR, that is fully active and has its cofactor tightly bound. A twin-arginine motif in the signal peptide directs it to a Sec-independent pathway by which it is translocated, in fully folded form, into the periplasm where it functions to produce sorbitol for osmoprotection. We have determined the crystal structures of four different forms of preGFOR, (i) oxidized preGFOR, with succinate bound in the active site, (ii) oxidized preGFOR with glycerol bound, (iii) reduced preGFOR in 0.3 M glucose, and (iv) reduced preGFOR in 1.5 M sorbitol, at resolutions of 2.2, 2.05, 2.5, and 2.6 A, respectively. In all four crystal structures, the signal peptide is disordered, implying a flexibility that may be important for its interaction with the translocation apparatus; a factor contributing to this disorder may be the high positive charge of the protein surface in the region where the signal peptide emerges. This may disfavor a stable association between the signal peptide and the rest of the protein. The crystal structures show that the mature enzyme portion of preGFOR is identical to native GFOR, in structure and cofactor binding, explaining the enzymatic activity of the precursor form. In the glycerol complex, preGFOR(gll), a bound glycerol molecule models the binding of the glucose substrate, with its O1 atom hydrogen bonded to the essential acid/base catalyst, Tyr269, and C1 only 3 A from C4 of the nicotinamide. In the glucose-soaked structure, preGFOR(glu), we identify a conformational change of the nearby Lys181 that probably results from the oxidation of glucose to gluconolactone, and functions to prevent rebinding of glucose prior to the binding of fructose. In this conformational change, the Lys181 side chain moves closer to the nicotinamide ring, stabilized by its increased negative charge.
About this StructureAbout this Structure
1H6C is a Single protein structure of sequence from Zymomonas mobilis. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structures of the precursor form of glucose-fructose oxidoreductase from Zymomonas mobilis and its complexes with bound ligands., Nurizzo D, Halbig D, Sprenger GA, Baker EN, Biochemistry. 2001 Nov 20;40(46):13857-67. PMID:11705375 Page seeded by OCA on Fri May 2 18:29:24 2008